Golf Ball with Scuff-Resistant Cover

ABSTRACT

Scuff-resistant golf ball covers and methods of manufacturing golf balls are described. The cover is made of a thermoplastic polymeric portion including at least one first, high molecular weight copolymer of ethylene/5-12 percent by weight acrylic or methacrylic acid or both/5-40 percent by weight alkyl acrylate or methacrylate or both; optionally at least one second, low molecular weight copolymer of ethylene/3-25 percent by weight acrylic or methacrylic acid or both; and a high molecular weight dipolymer of ethylene/acrylic acid that has a molar fraction of the acrylic acid monomer units within ±about 10% of a molar fraction of the α,β-ethylenically unsaturated carboxylic acid monomer units of the at least one first copolymer. The acid groups of all acid monomer units are neutralized 30% to about 75% on a molar basis by magnesium cations, calcium cations, zinc cations, or a combination of these cations.

The present application claims the benefit of U.S. ProvisionalApplication No. 61/980,849, filed Apr. 17, 2014.

FIELD

The disclosed technology relates to golf balls with scuff-resistantcovers made from ionomer resins and methods of making golf balls withscuff-resistant covers.

BACKGROUND

This section provides information helpful in understanding the disclosedtechnology but that is not necessarily prior art.

Golf ball covers formed from polyurethane compositions combine goodscuff resistance with a softness that enables spin control and goodplayability in “premium” balls for the more skilled player. Polyurethanecovers are low in resilience, however, and thermoset polyurethane coversare more difficult to process than thermoplastic ionomer resins. Thematerial costs are higher, as well, and therefore golf balls withpolyurethane covers are also more expensive to manufacture.

Ionomeric resins (ionomers) are useful materials for the construction ofgolf balls and other articles. Ionomers are ionic copolymers that areobtained by copolymerization of an olefin such as ethylene with anunsaturated carboxylic acid such as acrylic acid (AA), methacrylic acid(MAA), or maleic acid. Optionally, one or more softening monomers, suchas alkyl acrylates, may be included in the olefin-acid copolymer. Atleast a portion of the carboxylic acid groups in the copolymer areneutralized with a neutralizing agent to form carboxylate groups havingcounter cations, such as for example zinc cations or sodium cations. Theresulting ionomer is a thermoplastic resin exhibiting favorableproperties for use in golf balls. For example, golf balls constructedusing ionomeric materials have improved resilience and cut resistancedurability as compared with golf balls constructed with balata. As aresult of their resilience, toughness, durability and good flightcharacteristics, ionomers have become materials of choice for theconstruction of golf balls over the traditional balata,trans-polyisoprene, natural, and synthetic rubbers.

Harder ionomeric resins have been blended with softer ionomeric resinsto make a more durable golf ball cover material. U.S. Pat. Nos.4,884,814 and 5,120,791, for example, are directed to cover compositionscontaining blends of hard and soft ionomer resins. The hard copolymerstypically are ionomers of dipolymers made from an olefin and anunsaturated carboxylic acid and the soft copolymers typically areionomers of first copolymers made from an olefin, an unsaturatedcarboxylic acid, and an unsaturated carboxylic acid ester. While golfballs formed from hard-soft ionomer blends have good cut resistance,they tend to become scuffed more readily than covers made of hardionomer alone. U.S. Pat. No. 5,902,855 is directed to golf balls withscuff resistant covers comprising blends of ionomers with Shore Dhardness of about 40 to 64 units. Ichikawa et al., U.S. Pat. No.6,130,294 teaches blending a soft, magnesium-neutralizedethylene/acrylic acid, methacrylic acid, or both acrylic acid andmethacrylic acid/acrylate first copolymer ionomer with a hard,magnesium-neutralized ethylene/acrylic acid, methacrylic acid, or bothacrylic acid and methacrylic acid copolymer to make a blend having aShore D hardness of 44-60. A golf ball with this cover is said tominimize restitution loss and has increased initial velocity, spinreceptivity, good feel, and scuff resistance.

Bimodal ionomer compositions may also be used as scratch andscuff-resistant surface layers of a variety of articles. Chen, US Pat.Appl. Publ. 2004/0132552 discloses a cover with a “bimodal” ionomercomposition including the high molecular weight first copolymer and thelow molecular dipolymer achieves enhanced processability, resilience,stability, and scuff resistance. Chen, U.S. Patent ApplicationPublication No. 2009/0130355 discloses compositions that comprise anethylene α,β-ethylenically unsaturated C₃₋₈ carboxylic acid copolymerhaving weight average molecular weight (Mw) of about 80,000 to about500,000 Da (high molecular weight copolymer) and an ethyleneα,β-ethylenically unsaturated C₃₋₈ carboxylic acid copolymer having (Mw)of about 2,000 to about 30,000 Da (low molecular weight copolymer). Insome cases, however, these bimodal compositions are too soft to makegood golf ball covers. Bimodal ionomer compositions and their use ingolf balls are also described in Chen, U.S. Pat. Nos. 6,562,906;6,762,246; 7,037,967; 7,273,903; 7,488,778; 8,193,283; 8,410,219; and8,410,220.

Recently, Chen, US Pat. Appl. Publ. 2011/0306442 proposed a ternarymixture of a high molecular weight first copolymer of ethylene, a C₃-C₈α,β-ethylenically unsaturated carboxylic acid, and a softeningcomonomer; a high molecular weight dipolymer of ethylene and acrylic ormethacrylic acid; and a low molecular weight dipolymer of ethylene andacrylic or methacrylic acid, the mixture being neutralized at least 70%with predominantly zinc cations. Chen, U.S. Pat. No. 8,410,219 teachesthat the melt flow rate of such a ternary composition can be increasedby including non-zinc cations, but such a modification is not said to beeffective for improving scuff resistance.

Kasashima et al., U.S. Pat. No. 8,414,425 notes the difficulty ofproducing a soft golf ball having an excellent feel that achieves both agood flight performance and has an excellent durability to repeatedimpact. A softer cover produces a better feel, but lacks durability anddiminishes rebound, while a harder cover does not have the desired feeland is prone to early cracking. The Kasahima inventors focused on alayer underlying the cover for improving rebound, while filling anionomer-based cover with inorganic granular filler to achieve a desiredShore D hardness. Saski et al., U.S. Pat. No. 6,905,425, approach theproblem by including a significant amount of a thermoplastic styreneblock elastomer such as SBS.

Despite continuing efforts to bring the scuff resistance of the lessexpensive, more easily processed ionomer covers up to par withpolyurethane covers, substantial improvements in scuff resistance ofionomer covers have been elusive to date.

SUMMARY

This section provides a general summary of the disclosure and may not becomprehensive of its full scope or all of the disclosed features.

Disclosed are golf balls and methods of manufacturing the disclosed golfballs. The disclosed golf balls have a core and a cover having acomposition with a thermoplastic polymeric portion consisting of orconsisting essentially of a component (a) of (i) at least one firstcopolymer and, optionally, (ii) at least one second copolymer and acomponent (b) of a dipolymer. The at least one first copolymer (a)(i) isformed of ethylene monomer units, from about 5 to about 12 percent byweight of α,β-ethylenically unsaturated carboxylic acid monomer unitsselected from acrylic acid monomer units, methacrylic acid monomerunits, or a combination of acrylic acid monomer units and methacrylicacid monomer units, and from about 5 to about 40 percent by weight ofmonomer units of at least one alkyl acrylate or of at least one alkylmethacrylate or of a combination of at least one alkyl acrylate and atleast one alkyl methacrylate. The at least one first copolymer (a)(i)has a weight average molecular weight of from about 80,000 to about500,000 daltons. The at least one second copolymer (a)(ii) is formed ofethylene monomer units and from about 3 to about 25 percent by weight ofα,β-ethylenically unsaturated carboxylic acid monomer units selectedfrom acrylic acid monomer units, methacrylic acid monomer units, or acombination of acrylic acid monomer units and methacrylic acid monomerunits. The at least one second copolymer (a)(ii) has a weight averagemolecular weight of from about 2000 to about 30,000 daltons. The atleast one dipolymer (b) is formed of ethylene monomer units and acrylicacid monomer units. The at least one dipolymer (b) has a weight averagemolecular weight of from about 80,000 to about 500,000 daltons and has amolar fraction of acrylic acid monomer units within ±about 10% of amolar fraction of α,β-ethylenically unsaturated carboxylic acid monomerunits of the at least one first copolymer (a)(i). The molar fraction ofα,β-ethylenically unsaturated carboxylic acid monomer units of the firstcopolymer (a)(i) is the moles of α,β-ethylenically unsaturatedcarboxylic acid monomer units of all first copolymers (a)(i) divided bythe total moles of all constituent monomer units of all first copolymers(a)(i). Similarly, the molar fraction of acrylic acid monomer units ofthe dipolymer (b) is the moles of acrylic acid monomer units of alldipolymers (b) divided by the total moles of all constituent monomerunits of all dipolymers (b). The at least one first copolymer (a)(i) isfrom about 80 to 100 percent by weight of the sum of the weights of(a)(i) and (a)(ii). From about 30% to about 75% on a molar basis of allacid groups of (a) and (b) are neutralized with cations selected frommagnesium cations, calcium cations, zinc cations, and combinations ofthese cations. The α,β-ethylenically unsaturated carboxylic acid monomerof (a)(i) and the α,β-ethylenically unsaturated carboxylic acid monomerof (a)(ii) may be selected independently of each other. For example, onecould have only acrylic acid monomer units while the other has onlymethacrylic acid monomer units, or both could have all acrylic acidmonomer units or all methacrylic acid monomer units, or both could havea combination of acrylic acid and methacrylic acid monomer units inwhich the relative amounts of the acrylic acid monomer units and themethacrylic acid monomer units could be the same for both of ordifferent in each of the first copolymer (a)(i) and the second copolymer(a)(ii).

The disclosed method of manufacturing a golf ball comprises formingaround a core a cover from a thermoplastic polymeric portion consistingof or consisting essentially of a component (a) of (i) at least onefirst copolymer and, optionally, (ii) at least one second copolymer anda component (b) of a dipolymer. The at least one first copolymer (a)(i)is formed of ethylene monomer units, from about 5 to about 12 percent byweight of α,β-ethylenically unsaturated carboxylic acid monomer unitsselected from acrylic acid monomer units, methacrylic acid monomerunits, or a combination of acrylic acid monomer units and methacrylicacid monomer units, and from about 5 to about 40 percent by weight ofmonomer units of at least one alkyl acrylate or of at least one alkylmethacrylate or of a combination of at least one alkyl acrylate and atleast one alkyl methacrylate. The at least one first copolymer (a)(i)has a weight average molecular weight of from about 80,000 to about500,000 daltons. The at least one second copolymer (a)(ii) is formed ofethylene monomer units and from about 3 to about 25 percent by weight ofα,β-ethylenically unsaturated carboxylic acid monomer units selectedfrom acrylic acid monomer units, methacrylic acid monomer units, or acombination of acrylic acid monomer units and methacrylic acid monomerunits. The at least one second copolymer (a)(ii) has a weight averagemolecular weight of from about 2000 to about 30,000 daltons. The atleast one dipolymer (b) is formed of ethylene monomer units and acrylicacid monomer units. The at least one dipolymer (b) has a weight averagemolecular weight of from about 80,000 to about 500,000 daltons and has amolar fraction of acrylic acid monomer units within ±about 10% of amolar fraction of α,β-ethylenically unsaturated carboxylic acid monomerunits of the at least one first copolymer (a)(i). The molar fraction ofα,β-ethylenically unsaturated carboxylic acid monomer units of the firstcopolymer (a)(i) is the moles of α,β-ethylenically unsaturatedcarboxylic acid monomer units of all first copolymers (a)(i) divided bythe total moles of all constituent monomer units of all first copolymers(a)(i). Similarly, the molar fraction of acrylic acid monomer units ofthe dipolymer (b) is the moles of acrylic acid monomer units of alldipolymers (b) divided by the total moles of all constituent monomerunits of all dipolymers (b). The at least one first copolymer (a)(i) isfrom about 80 to 100 percent by weight of the sum of the weights of(a)(i) and (a)(ii). From about 30% to about 75% on a molar basis of allacid groups of (a) and (b) are neutralized with cations selected frommagnesium cations, calcium cations, zinc cations, and combinations ofthese cations. The α,β-ethylenically unsaturated carboxylic acid monomerof (a)(i) and the α,β-ethylenically unsaturated carboxylic acid monomerof (a)(ii) may be selected independently of each other. For example, onecould have only acrylic acid monomer units while the other has onlymethacrylic acid monomer units, or both could have all acrylic acidmonomer units or all methacrylic acid monomer units, or both could havea combination of acrylic acid and methacrylic acid monomer units inwhich the relative amounts of the acrylic acid monomer units and themethacrylic acid monomer units could be the same for both of ordifferent in each of the first copolymer (a)(i) and the second copolymer(a)(ii).

The golf ball cover's component (a) can be or can consist essentially ofthe at least one first copolymer (a)(i). Alternatively, the golf ballcover's component (a) can include the at least one second copolymer(a)(ii), which may be present in from a finite amount more than zero toabout 20 percent by weight of the sum of the weights of the at least onefirst copolymer (a)(i) and the at least one second copolymer (a)(ii).Copolymer (a)(i) can be 100 percent by weight and copolymer (a)(ii) 0percent by weight of the sum of the weights of (a)(i) and (a)(ii). Inother embodiments, the at least one second copolymer (a)(ii) can be fromabout 5 to about 20 percent by weight, based on the sum of the weightsof (a)(i) and (a)(ii) or the at least one second copolymer (a)(ii) canbe from about 5 to about 15 percent by weight, based on the sum of theweights of (a)(i) and (a)(ii). The at least one dipolymer (b) can befrom about 10 to about 90 percent by weight, based on the combinedweights of components (a) (the at least one first copolymer (a)(i) and,if present, the at least one second copolymer (a)(ii)) and (b) (the atleast one dipolymer (b)). The at least one dipolymer (b) can be fromabout 30 to about 65 percent by weight, based on the combined weights ofcomponents (a) (the at least one first copolymer (a)(i) and, if present,the at least one second copolymer (a)(ii)) and (b) (the at least onedipolymer (b)).

The at least one first copolymer (a)(i) monomer units of at least onealkyl acrylate or of at least one alkyl methacrylate or of a combinationof at least one alkyl acrylate and at least one alkyl methacrylate canbe or include n-butyl acrylate monomer units or isobutyl acrylatemonomer units, or both. The at least one first copolymer (a)(i) can beor include a copolymer selected from the group consisting of copolymersof ethylene/acrylic acid/n-butyl acrylate, copolymers ofethylene/methacrylic acid/n-butyl acrylate, copolymers ofethylene/methacrylic acid/isobutyl acrylate, copolymers ofethylene/acrylic acid/isobutyl acrylate, all of which may be used in anycombination.

In various embodiments, the α,β-ethylenically unsaturated carboxylicacid monomer units of one or both of the at least one first copolymer(a)(i) and the at least one second copolymer (a)(ii) are acrylic acidmonomer units.

In various embodiments, the neutralizing cations are selected frommagnesium cations, calcium cations, and combinations thereof. In certainembodiments, the neutralizing cations are all calcium cations. Theneutralizing metal cations can all be calcium cations. The neutralizingmetal cations can all be magnesium cations. The neutralizing metalcations can all be calcium cations. The neutralizing metal cations canall be zinc cations. For example, about 50% to 100% on a molar basis ofthe neutralizing cations can be magnesium cations, calcium cations, or acombination of magnesium and calcium cations. From about 50% to about100% on a molar basis of the neutralizing cations can be magnesiumcations. From about 50% to 100% on a molar basis of the neutralizingcations can be calcium cations. From about 50% to about 100% on a molarbasis of the neutralizing metal cations can be zinc cations.

The at least one first copolymer (a)(i) can have from about 8 to about12 percent by weight of α,β-ethylenically unsaturated carboxylic acidmonomer units.

The at least one dipolymer (b) can have a molar fraction of acrylic acidmonomer units within ±about 5% of a molar fraction of α,β-ethylenicallyunsaturated carboxylic acid monomer units of the at least one firstcopolymer (a)(i). The at least one dipolymer (b) can have a molarfraction of acrylic acid monomer units within ±about 3% of a molarfraction of α,β-ethylenically unsaturated carboxylic acid monomer unitsof the at least one first copolymer (a)(i).

The at least one first copolymer (a)(i) can have from about 8 to about12 percent by weight of α,β-ethylenically unsaturated carboxylic acidmonomer units, and the at least one dipolymer (b) can have a molarfraction of acrylic acid monomer units within ±about 3% of a molarfraction of α,β-ethylenically unsaturated carboxylic acid monomer unitsof the at least one first copolymer (a)(i). The at least one secondcopolymer (a)(ii) can have from about 5 to about 20 weight percent ofα,β-ethylenically unsaturated carboxylic acid monomer units. The atleast one second copolymer (a)(ii) can have from about 8 to about 18weight percent of α,β-ethylenically unsaturated carboxylic acid monomerunits. The at least one first copolymer (a)(i) can have from about 8 toabout 12 weight percent of α,β-ethylenically unsaturated carboxylic acidmonomer units, and the at least one second copolymer (a)(ii) can havefrom about 8 to about 18 weight percent of α,β-ethylenically unsaturatedcarboxylic acid monomer units. The at least one first copolymer (a)(i)can have from about 8 to about 12 weight percent of α,β-ethylenicallyunsaturated carboxylic acid monomer units, the at least one secondcopolymer (a)(ii) can have from about 8 to about 18 weight percent ofα,β-ethylenically unsaturated carboxylic acid monomer units. and the atleast one dipolymer (b) can have a molar fraction of acrylic acidmonomer units within ±about 3% of a molar fraction of α,β-ethylenicallyunsaturated carboxylic acid monomer units of the at least one firstcopolymer (a)(i).

The weight average molecular weight of the at least one first copolymer(a)(i) can be from about 200,000 to about 400,000 daltons. The at leastone first copolymer can have a weight average molecular weight of fromabout 150,000 daltons to about 350,000 daltons. The at least one firstcopolymer can have a polydispersity (Mw/Mn) of from about 1 to about 15.The at least one first copolymer can have a weight average molecularweight of from about 150,000 daltons to about 350,000 daltons, apolydispersity (Mw/Mn) of from about 1 to about 3, and can have fromabout 8 to about 9 wt % of the α,β-ethylenically unsaturated carboxylicacid monomer units present.

The weight average molecular weight of the at least one second copolymer(a)(ii) can be from about 5000 daltons to about 25,000 daltons. Thenumber average molecular weight of the at least one second copolymer canbe from about 10,000 daltons to about 20,000 daltons. The polydispersity(Mw/Mn) of the second copolymer can be from about 1 to about 15. Thepolydispersity of the second copolymer can be from about 1 to about 3.The number average molecular weight of the at least one second copolymercan be from about 10,000 daltons to about 20,000 daltons, and thepolydispersity of the second copolymer can be from about 1 to about 3.

The weight average molecular weight of the at least one dipolymer (b)can be from about 200,000 to about 400,000 daltons. The weight averagemolecular weight of the at least one dipolymer (b) can be from about150,000 daltons to about 350,000 daltons. The at least one dipolymer (b)can have a polydispersity of from about 1 to about 15. The at least onedipolymer (b) can have a polydispersity of about 1 to about 3. Theweight average molecular weight of the at least one dipolymer (b) can befrom about 150,000 daltons to about 350,000 daltons, and apolydispersity of about 1 to about 3.

The weight average molecular weight of the at least one first copolymer(a)(i) can be from about 200,000 to about 400,000 daltons, and theweight average molecular weight of the at least one dipolymer (b) can befrom about 200,000 to about 400,000 daltons.

The cover of the golf ball can have a thickness of from about 1 mm toabout 3 mm.

An “ethylenically unsaturated bond” is a carbon-to-carbon double bond.“A,” “an,” “the,” “at least one,” and “one or more” are usedinterchangeably to indicate that at least one of the item is present; aplurality of such items may be present unless the context clearlyindicates otherwise. All numerical values of parameters (e.g., ofquantities or conditions) in this specification, including the appendedclaims, are to be understood as being modified in all instances by theterm “about” whether or not “about” actually appears before thenumerical value. “About” indicates that the stated numerical valueallows some slight imprecision (with some approach to exactness in thevalue; approximately or reasonably close to the value; nearly). If theimprecision provided by “about” is not otherwise understood in the artwith this ordinary meaning, then “about” as used herein indicates atleast variations that may arise from ordinary methods of measuring andusing such parameters. In addition, disclosure of ranges includesdisclosure of all values and further divided ranges within the entirerange. Each value within a range and the endpoints of a range are herebyall disclosed as separate embodiment. The ranges set forth hereininclude their endpoints unless expressly stated otherwise. When anamount, concentration, or other value or parameter is given as a range,one or more preferred ranges or a list of upper preferable values andlower preferable values, this is to be understood as specificallydisclosing all ranges formed from any pair of any upper range limit orpreferred value and any lower range limit or preferred value, regardlessof whether such pairs are separately disclosed. The scope of theinvention is not limited to the specific values recited when defining arange. In this description of the invention, for convenience, “polymer”and “resin” are used interchangeably to encompass resins, oligomers, andpolymers. The terms “comprises,” “comprising,” “including,” and“having,” are inclusive and therefore specify the presence of stateditems, but do not preclude the presence of other items. As used in thisspecification, the term “or” includes any and all combinations of one ormore of the listed items. Further, as used herein, the terminology “atleast” is equivalent to “greater than or equal to,” and the terminology“up to” is equivalent to “less than or equal to.”

A description of a copolymer with reference to its constituentcomonomers or to the amounts of its constituent comonomers means thatthe copolymer contains copolymerized units of the specified comonomerswhich may be contained in a specified amount. The term “dipolymer”refers to polymers consisting essentially of two different copolymerizedmonomers and the term “copolymer” refers to polymers having differentcopolymerized monomers.

The term “Mw” means weight average molecular weight and the term “Mn”means number average molecular weight. In this description, “lowmolecular weight” is used to refer to polymers that have a weightaverage molecular weight (Mw) of from about 2000 to about 30,000 daltonsand “high molecular weight” is used to refer to polymers that have amolecular weight (Mw) of from about 80,000 to about 500,000 daltons.Number average molecular weight and weight average molecular weight aredetermined by gel permeation chromatography (GPC) using polystyrenestandards.

It should be understood that the description and specific examples areintended for purposes of illustration only and are not intended to limitthe scope of the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings illustrate some aspects of the disclosed technology.

The FIGURE is a schematic, cross-sectional view of a golf ball.

The parts of the FIGURE are not necessarily to scale.

DETAILED DESCRIPTION

A detailed description including exemplary, nonlimiting embodimentsfollows. Unless stated otherwise, amount are by weight.

The disclosed golf ball has an ionomer-resin cover with improved scuffresistance. The golf ball has a core, the cover, and optionally one ormore intermediate layers between the core and the cover. For example,the golf ball may be a four-piece golf ball such as the one illustratedin the FIGURE, in which a golf ball 10 includes a core 12, a cover 18that forms an outermost layer of golf ball 10, and intermediate layers14, 16. The cover 18 is formed from a composition having the disclosedthermoplastic polymeric portion consisting essentially of a highmolecular weight first copolymer (a)(i) formed of ethylene monomerunits, about 5 to about 12 percent by weight α,β-ethylenicallyunsaturated carboxylic acid monomer units selected from acrylic acidmonomer units, methacrylic acid monomer units, and combinations ofacrylic acid and methacrylic acid monomer units, and about 3 to about 40weight percent of at least one member selected from the group consistingof alkyl acrylate monomer units, alkyl methacrylate monomer units, andcombinations of alkyl acrylate monomer units, alkyl methacrylate monomerunits; a high molecular weight dipolymer (b) formed of ethylene monomerunits and acrylic acid monomer units having a molar fraction of acrylicacid monomer units within ±about 10% of a molar fraction ofα,β-ethylenically unsaturated carboxylic acid monomer in the at leastone first copolymer (a)(i); and, optionally, a low molecular weightsecond copolymer (a)(ii) formed of ethylene monomer units and about 3 toabout 25 percent by weight α,β-ethylenically unsaturated carboxylic acidmonomer units selected from selected from acrylic acid monomer units,methacrylic acid monomer units, and combinations of acrylic acid andmethacrylic acid monomer units. The at least one second copolymer(a)(ii) may be included in the thermoplastic polymeric portion in anamount of 0 to about 20 percent by weight based on the combined weightof (a) the first and second copolymers in the thermoplastic polymericportion. The cover composition comprises the thermoplastic polymericportion and may also include nonpolymeric materials, for examplepigment, filler, and other additives in any combination, includingfunctional additives such as reinforcing chopped fibers, aramide fibersand micropulps, organo-clays to achieve exfoliated nano-platlets,nano-silicas, and so on, which may be used in any combination and whichmay be present in the cover to further enhance the mechanicalproperties, such as stiffness, scuff resistance, or wear resistance.

The at least one high molecular weight first copolymer (a)(i) and the atleast one high molecular weight dipolymer (b) each have a weight averagemolecular weight of from about 80,000 to about 500,000 daltons. The lowmolecular weight at least one second copolymer (a)(ii) has a weightaverage molecular weight of from about 2000 to about 30,000 daltons.

While the FIGURE generally illustrates a ball 10 with a four-piececonstruction, the disclosed technology may be used to prepare atwo-piece ball with a core and the cover, a three-piece ball with acore, an intermediate layer, and the cover, as well as balls with fiveor more pieces that include the disclosed cover.

The cover 18 defines an outermost structural layer of the ball 10 andgenerally includes any desired number of dimples including, for example,between 280 and 432 total dimples, and in some examples, between 300 and392 total dimples, and typically between 298 to 360 total dimples. Asknown in the art, the inclusion of dimples generally decreases theaerodynamic drag of the ball, which may provide for greater flightdistances when the ball is properly struck. In golf ball 10, each layer(including the center 12, cover 18, and intermediate layers 14, 16) issubstantially concentric with every other layer such that all layersshare a common geometric center.

The golf ball cover is made from a thermoplastic, ionomeric composition.The thermoplastic polymeric portion of the golf ball cover consistsessentially of, or consists of, (a) at least one first copolymer (a)(i)and optionally at least one second copolymer (a)(ii) and (b) at leastone dipolymer. The component (a) is from about 10 to about 90 percent byweight, based on total weight of (a) and (b).

The component (a) consists of from about 80 to 100 percent by weight,based on a total weight of (a)(i) and (a)(ii), of the at least one firstcopolymer (a)(i) and from about 0 to about 20 percent by weight, basedon a total weight of (a)(i) and (a)(ii), of the at least one secondcopolymer (a)(ii). The at least one first copolymer (a)(i) consists ofethylene monomer units, from about 5 to about 12 percent by weight ofα,β-ethylenically unsaturated carboxylic acid monomer units selectedfrom acrylic acid monomer units, methacrylic acid monomer units, or bothacrylic acid and methacrylic acid monomer units, and from about 5 toabout 40 percent by weight of alkyl acrylate monomer units, alkylmethacrylate monomer units, or a combination alkyl acrylate monomerunits and alkyl methacrylate monomer units. The at least one secondcopolymer consists of ethylene monomer units and from about 3 to about25 percent by weight of α,β-ethylenically unsaturated carboxylic acidmonomer units selected from acrylic acid monomer units, methacrylic acidmonomer units, or both acrylic acid and methacrylic acid monomer units.

The at least one dipolymer consists of ethylene monomer units andacrylic acid monomer units. The molar fraction of acrylic acid monomerunits in the at least one dipolymer (b) is within ±about 10% of themolar fraction of α,β-ethylenically unsaturated carboxylic acid monomerunits in the at least one first copolymer (a)(i). The molar fraction ofα,β-ethylenically unsaturated carboxylic acid monomer units of the firstcopolymer (a)(i) is the moles of α,β-ethylenically unsaturatedcarboxylic acid monomer units of all first copolymers (a)(i) divided bythe total moles of all constituent monomer units of all first copolymers(a)(i). Similarly, the molar fraction of acrylic acid monomer units ofthe dipolymer (b) is the moles of acrylic acid monomer units of alldipolymers (b) divided by the total moles of all constituent monomerunits of all dipolymers (b).

The first copolymer (a)(i) has a weight average molecular weight of fromabout 80,000 to about 500,000 daltons, The second copolymer (a)(ii) hasa weight average molecular weight of from about 2000 to about 30,000daltons. The dipolymer (b) has a weight average molecular weight of fromabout 80,000 to about 500,000 daltons. From about 30% to about 75% on amolar basis of the combined carboxyl groups of the α,β-ethylenicallyunsaturated carboxylic acid monomer units of (a) and the acrylic acidmonomer units of (b) are neutralized with cations selected from thegroup consisting of magnesium cations, calcium cations, zinc cations,and combinations thereof.

The first copolymer has or first copolymers (a)(i) have theα,β-ethylenically unsaturated carboxylic acid monomer units selectedfrom the group consisting of acrylic acid monomer units, methacrylicacid monomer units, and combinations of acrylic acid monomer units andmethacrylic acid monomer units present in an amount of from about 5 toabout 12 percent by weight based on total first copolymer weight. In oneexample, the first copolymer may have from about 5 percent by weight orfrom about 6 percent by weight or from about 7 percent by weight or fromabout 8 percent by weight and up to about 12 percent by weight or up toabout 11 percent by weight or up to about 10 percent by weight of thecopolymerized acrylic acid monomer units, methacrylic acid monomerunits, or both acrylic acid and methacrylic acid monomer units. In anexample, the first copolymer may have from about 5 percent by weight toabout 11 percent by weight of the α,β-ethylenically unsaturatedcarboxylic acid monomer units present. In another example, the firstcopolymer may have from about 6 percent by weight to about 11 percent byweight of the α,β-ethylenically unsaturated carboxylic acid monomerunits present. In another example, the first copolymer may have fromabout 6 percent by weight to about 10 percent by weight of theα,β-ethylenically unsaturated carboxylic acid monomer units present. Instill another example, the first copolymer may have from about 7 percentby weight to about 11 percent by weight of the α,β-ethylenicallyunsaturated carboxylic acid monomer units present. In yet anotherexample, the first copolymer may have from about 7 percent by weight toabout 10 percent by weight of the α,β-ethylenically unsaturatedcarboxylic acid monomer units present. Still further, the firstcopolymer may have from about 8 percent by weight to about 10 percent byweight or from about 8 to about 9 percent by weight of theα,β-ethylenically unsaturated carboxylic acid monomer units present.

The copolymerized α,β-ethylenically unsaturated carboxylic acid monomerunits of the first copolymer may be all acrylic acid monomer units, allmethacrylic acid monomer units, or a combination of acrylic acid monomerunits and methacrylic acid monomer units. When a combination of acrylicacid monomer units and methacrylic acid monomer units are used, the atleast one first copolymer may be one first copolymer or a plurality offirst copolymers that contain both acrylic acid monomer units andmethacrylic acid monomer units, optionally in addition to one or morefirst copolymers that contain only acrylic acid monomer units or thatcontain only methacrylic acid monomer units. Alternatively, when acombination of acrylic acid monomer units and methacrylic acid monomerunits are present in the at least one first copolymer (a)(i), thecover's thermoplastic polymeric portion may contain a plurality of firstcopolymers (a)(i), at least one of which contains only acrylic acidmonomer units and at least one of which contains only methacrylic acidmonomer units.

The first copolymer (a)(i) includes or first copolymers (a)(i) includefrom about 5 to about 40 percent by weight of alkyl acrylate monomerunits, alkyl methacrylate monomer units, or both alkyl acrylate monomerunits and alkyl methacrylate monomer units monomer units. Nonlimitingexamples of suitable alkyl acrylates and alkyl methacrylates that may becopolymerized with the ethylene and α,β-ethylenically unsaturatedcarboxylic acid to form the first copolymer (a)(i) include alkyl estersof acrylic acid and methacrylic acid in which the alkyl group has fromone to about 8 carbon atoms. In various embodiments, the alkyl group ofthe ester may have from 2 to 8 carbon atoms. In other examples, thealkyl group of the ester may have from 2 to 7 carbon atoms. In stillother examples, the alkyl group of the ester may have from 2 to 6 carbonatoms. The first copolymer (a)(i) may contain the alkyl acrylate monomerunits and alkyl methacrylate monomer units in any combination and, foreach combination, in any proportion of the various alkyl acrylatemonomer units and alkyl methacrylate monomer units. Yet further, thealkyl group of the ester may have 3 or 4 or 5 or 6 carbon atoms, forinstance the alkyl group of the ester may have 3 or 4 carbon atoms.Nonlimiting examples of suitable alkyl acrylates and alkyl methacrylatesthat may be polymerized to form copolymerized units of the firstcopolymer (a)(i) are methyl acrylate, methyl methacrylate, ethylacrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate,isopropyl acrylate, isopropyl methacrylate, butyl acrylate, butylmethacrylate, isobutyl acrylate, isobutyl methacrylate, sec-butylacrylate, sec-butyl methacrylate, tert-butyl acrylate, tert-butylmethacrylate, hexyl acrylate, hexyl methacrylate, 2-ethylhexyl acrylate,and 2-ethylhexyl methacrylate, which may be used in any combination.

The alkyl acrylate monomer units, alkyl methacrylate monomer units, orboth alkyl acrylate monomer units and alkyl methacrylate monomer unitsmay be present in a weight percentage of the first copolymer (a)(i) in arange of from about 5 or about 6 or about 7 or about 8 or about 10 orabout 12 or about 15 or about 20 weight percent of the of the firstcopolymer (a)(i) and an upper limit of about 23 or about 25 or about 30or about 35 or about 40 weight percent of the first copolymer (a)(i).Particular pairs of lower and upper range limits for the alkyl acrylate,alkyl methacrylate, or both alkyl acrylate monomer units and alkylmethacrylate monomer units that may be mentioned include from about 10weight percent to about 40 weight percent, from about 5 weight percentto about 35 weight percent, from about 10 weight percent to about 35weight percent, from about 15 weight percent to about 40 weight percent,from about 15 weight percent to about 35 weight percent, and from about20 weight percent to about 35 weight percent, of the first copolymer(a)(i)

Nonlimiting specific examples of the at least one first copolymers(a)(i) include first copolymers of ethylene/acrylic acid/n-butylacrylate, ethylene/methacrylic acid/n-butyl acrylate,ethylene/methacrylic acid/isobutyl acrylate, ethylene/acrylicacid/isobutyl acrylate, ethylene/acrylic acid/hexyl acrylate,ethylene/methacrylic acid/hexyl acrylate, ethylene/acrylic acid/hexylmethacrylate, ethylene/methacrylic acid/hexyl methacrylate,ethylene/acrylic acid/methyl methacrylate, ethylene/acrylic acid/methylacrylate, ethylene/methacrylic acid/methyl acrylate, andethylene/methacrylic acid/methyl methacrylate. In various embodiment,the at least one first copolymer (a)(i) may be one or more ofethylene/acrylic acid/n-butyl acrylate, ethylene/methacrylicacid/n-butyl acrylate, ethylene/methacrylic acid/isobutyl acrylate,ethylene/acrylic acid/isobutyl acrylate.

The first copolymer (a)(i) has or first copolymers (a)(i) each has aweight average molecular weight of from about 80,000 daltons or fromabout 100,000 daltons or from about 120,000 daltons or from about150,000 daltons to about 300,000 daltons or to about 350,000 daltons orto about 400,000 daltons or to about 450,000 daltons or to about 500,000daltons. In various embodiments, the first copolymer (a)(i) can have orfirst copolymers (a)(i) each can have a weight average molecular weightof from about 80,000 daltons to about 450,000 daltons or from about100,000 daltons to about 450,000 daltons or from about 120,000 daltonsto about 400,000 daltons or from about 150,000 daltons to about 350,000daltons. It or they each can have a polydispersity (Mw/Mn) of from about1 to about 15 or a polydispersity of from about 1 to about 10 or apolydispersity of from about 1 to about 5 or a polydispersity of fromabout 1 to about 3.

The second copolymer or copolymers (a)(ii) may have theα,β-ethylenically unsaturated carboxylic acid monomer units selectedfrom the group consisting of acrylic acid monomer units, methacrylicacid monomer units, and combinations of acrylic acid monomer units andmethacrylic acid monomer units present in an amount in a range having alower limit of about 3 or about 4 or about 5 or about 6 or about 7 orabout 8 or about 9 or about 10 weight percent and an upper limit ofabout 25 or about 23 or about 20 or about 18 or about 16 weight percentbased on the total weight of the second copolymer (a)(ii). For example,the second copolymer or copolymers (a)(ii) may have theα,β-ethylenically unsaturated carboxylic acid monomer units present inan amount of from about 3 to about 25 weight percent or present in anamount of from about 5 to about 20 weight percent. In other embodiments,the second copolymer or copolymers (a)(ii) may have theα,β-ethylenically unsaturated carboxylic acid monomer units present inan amount of from about 7 to about 18 weight percent or present in anamount of from about 8 to about 18 weight percent.

The copolymerized α,β-ethylenically unsaturated carboxylic acid monomerunits of the second copolymer (a)(ii) may be all acrylic acid monomerunits, all methacrylic acid monomer units, or a combination of acrylicacid monomer units and methacrylic acid monomer units. When acombination of acrylic acid monomer units and methacrylic acid monomerunits are used, the at least one second copolymer (a)(ii) may be onesecond copolymer (a)(ii) or a plurality of second copolymers (a)(ii)that contain both acrylic acid monomer units and methacrylic acidmonomer units, optionally in addition to one or more second copolymers(a)(ii) that contain only acrylic acid monomer units or that containonly methacrylic acid monomer units. Alternatively, when a combinationof acrylic acid monomer units and methacrylic acid monomer units arepresent in the at least one second copolymer (a)(ii), the cover'sthermoplastic polymeric portion may contain a plurality of secondcopolymers (a)(ii), at least one of which contains only acrylic acidmonomer units and at least one of which contains only methacrylic acidmonomer units.

The amount of acrylic acid monomer units, methacrylic acid monomerunits, or both acrylic acid monomer units and methacrylic acid monomerunits in the second copolymer or copolymers (a)(ii) is independent ofthe amount of acrylic acid monomer units, methacrylic acid monomerunits, or both acrylic acid monomer units and methacrylic acid monomerunits in the first copolymer or first copolymers (a)(i) and alsoindependent of the amount of acrylic acid monomer units in the dipolymeror dipolymers (b).

The second copolymer (a)(ii) has or the second copolymers (a)(ii) eachhas a weight average molecular weight of from about 2000 daltons or fromabout 3000 daltons or from about 5000 daltons or from about 8000 daltonsto about 30,000 daltons or to about 28,000 daltons or to about 25,000daltons or to about 20,000 daltons or to about 18,000 daltons. Invarious embodiments, the second copolymer (a)(ii) has or each of thesecond copolymers (a)(ii) has a weight average molecular weight of fromabout 2000 daltons to about 30,000 daltons or from about 5000 daltons toabout 25,000 daltons or from about 10,000 daltons to about 25,000daltons or from about 10,000 daltons to about 20,000 daltons. It or theyeach can have a polydispersity Mw/Mn) of from about 1 to about 15 or apolydispersity of from about 1 to about 10 or a polydispersity of fromabout 1 to about 5 or a polydispersity of from about 1 to about 3.

The second copolymer (a)(ii) is or second copolymers (a)(ii) areoptional components and thus are not required for the cover's polymericportion, but when present the second copolymer (a)(ii) is or secondcopolymers (a)(ii) are present in a range of from a finite amount orfrom about 1 percent by weight or from about 2 percent by weight or fromabout 3 percent by weight or from about 5 percent by weight or fromabout 7 percent by weight or from about 10 percent by weight up to about20 percent by weight or up to about 18 percent by weight or up to about16 percent by weight or up to about 15 percent by weight, based in eachcase on the sum of the weights of (a)(i) and (a)(ii). For example, thesecond copolymer (a)(ii) or second copolymers (a)(ii) may be present ina range of from about 1 percent by weight to about 20 percent by weight,based on the sum of the weights of (a)(i) and (a)(ii). In otherexamples, the second copolymer (a)(ii) or second copolymers (a)(ii) maybe present in a range of from about 5 percent by weight to about 20percent by weight or in a range of from about 5 percent by weight toabout 15 percent by weight, based on the sum of the weights of (a)(i)and (a)(ii). Conversely, when the second copolymer (a)(ii) is or secondcopolymers (a)(ii) are included in the cover's polymeric portion, thefirst copolymer (a)(i) is or first copolymers (a)(i) are collectivelypresent in a range of from about 80 percent by weight or from about 82percent by weight or from about 84 percent by weight or from about 85percent by weight up to about 100 percent by weight or up to about 99percent by weight or up to about 97 percent by weight or up to about 95percent by weight or up to about 93 percent by weight or up to about 90percent by weight, based in each case on the sum of the weights of(a)(i) and (a)(ii). For example, the first copolymer (a)(i) or firstcopolymers (a)(i) may be present in a range of from about 80 percent byweight to about 99 percent by weight, based on the sum of the weights of(a)(i) and (a)(ii). In other examples, the first copolymer (a)(i) orfirst copolymers (a)(i) may be present in a range of from about 80percent by weight to about 95 percent by weight or in a range of fromabout 75 percent by weight to about 95 percent by weight, based on thesum of the weights of (a)(i) and (a)(ii).

The polymeric portion of the cover also includes at least one dipolymerof ethylene and acrylic acid (b). The molar fraction of acrylic acidmonomer units of the at least one dipolymer (b) is within ±about 10% of,or within ±about 8% of, or within ±about 6% of, or within ±about 5% of,or within ±about 4% of, or within ±about 3% of, or within ±about 2% of,or within ±about 1% of, or within ±about 0.5% of, or about the same asthe molar fraction of α,β-ethylenically unsaturated carboxylic acidmonomer units in the at least one first copolymer (a)(i). When there isa plurality of dipolymers (b), the molar fraction of acrylic acidmonomer units is the average molar fraction of acrylic acid monomerunits for all of the dipolymers (b). That is, it is the moles of allacrylic acid monomer units in all dipolymers (b) divided by the totalmoles of all the constituent monomer units of all dipolymers (b).Likewise, when there is a plurality of first copolymers (a)(i), themolar fraction of α,β-ethylenically unsaturated carboxylic acid monomerunits is the average molar fraction for all of the first copolymers(a)(i), which is the moles of all α,β-ethylenically unsaturatedcarboxylic acid monomer units in all first copolymers (a)(i) divided bythe total moles of all the constituent monomer units of all firstcopolymers (a)(i).

The dipolymer (b) has or each of the dipolymers (b) has a weight averagemolecular weight of from about 80,000 daltons or from about 100,000daltons or from about 120,000 daltons or from about 150,000 daltons toabout 300,000 daltons or to about 350,000 daltons or to about 400,000daltons or to about 450,000 daltons or to about 500,000 daltons. Invarious embodiments, the dipolymer (b) has or each of the dipolymers (b)has a weight average molecular weight of from about 80,000 daltons toabout 450,000 daltons or from about 100,000 daltons to about 450,000daltons or from about 120,000 daltons to about 400,000 daltons or fromabout 1500,000 daltons to about 350,000 daltons. It or they each canhave a polydispersity (Mw/Mn) of from about 1 to about 15 or apolydispersity of from about 1 to about 10 or a polydispersity of fromabout 1 to about 5 or a polydispersity of from about 1 to about 3. Themolecular weight and polydispersity of the dipolymer (b) or of eachdipolymer (b) is independent of the molecular weight and polydispersityof the first copolymer (a)(i) or of any of the first copolymers (a)(i).

The polymeric portion of the cover or composition from which the coveris made has from about 10 percent by weight or from about 15 percent byweight or from about 20 percent by weight or from about 25 percent byweight or from about 30 percent by weight or from about 35 percent byweight or from about 40 percent by weight or from about 45 percent byweight up to about 90 percent by weight or up to about 85 percent byweight or up to about 80 percent by weight or up to about 75 percent byweight or up to about 70 percent by weight or up to about 65 percent byweight or up to about 60 percent by weight or up to about 55 percent byweight of the at least one dipolymer (b) based on the combined weightsof components (a) (the first copolymer or first copolymers (a)(i) and,if present, the dipolymer or dipolymers (a)(ii)) and (b) (the at leastone dipolymer (b)). While the amount of the at least one dipolymer (b)may be in a range having a lower limit selected from any of these justgiven and a higher limit selected from any of these just given, examplesof ranges for the amount of the at least one dipolymer (b) are fromabout 10 percent by weight to about 90 percent by weight or from about20 percent by weight to about 80 percent by weight or from about 25percent by weight to about 75 percent by weight or from about 30 percentby weight to about 65 percent by weight, in each case based on thecombined weights of components (a) and (b).

Methods of preparing the at least one first copolymer (a)(i), at leastone second copolymer (a)(ii), and at least one dipolymer (b) are knownand include, for example continuous polymerization in by use of“co-solvent technology” as described in U.S. Pat. No. 5,028,674, whichis incorporated by reference, as well as batch polymerization insolution or neat (particularly for the low molecular weight secondcopolymer (a)(ii)) or by emulsion polymerization (particularly for thehigh molecular weight polymers). Polymerization may be carried out usingany convenient free radical initiator or initiators, for example.

From about 30% to about 75% on a molar basis of the combined carboxylgroups of the α,β-ethylenically unsaturated carboxylic acid monomerunits of components (a) and of the acrylic acid monomer units of (b)(that is, the at least one first copolymer (a)(i), the at least onesecond copolymer (a)(ii) (if present) and the at least one dipolymer(b)) are neutralized with cations selected from the group consisting ofmagnesium cations, calcium cations, zinc cations, and combinationsthereof. In various embodiments, the neutralizing cations are selectedfrom magnesium cations, calcium cations, and combinations thereof. Incertain embodiments, the neutralizing cations are calcium cations.

Ionic compounds that may be used as sources of the neutralizing cationsinclude formates, acetates, nitrates, carbonates, hydrogen carbonates,oxides, hydroxides or alkoxides. The amount of ionic compound capable ofneutralizing a certain number of carboxyl groups (referred to herein as“% nominal neutralization” or “nominally neutralized”) may be determinedby simple stoichiometric principles. When an amount of cation sufficientto neutralize a target amount of carboxyl groups is made available in amelt of first copolymer (a)(i) or second copolymer (a)(ii) or component(a) or component (b) or combination of components (a) and (b) of thethermoplastic portion, it is assumed that, in aggregate, the indicatedlevel of nominal neutralization is achieved.

The at least one copolymer (a)(i), at least one copolymer (a)(ii), andat least one dipolymer (b) can be neutralized separately with differentcations or the same cation to the same or different degrees ofneutralization, and then subsequently melt blended into the finalcomposition at the desired proportion and further neutralized ifdesired. The range of neutralization may on a molar basis for the atleast one copolymer (a)(i), at least one copolymer (a)(ii), and at leastone dipolymer (b) may be independent from the range of neutralization offrom 35% to 75% on a molar basis, for the combination of the at leastone copolymer (a)(i), at least one copolymer (a)(ii), and at least onedipolymer (b) in the cover composition. For example, the range ofneutralization can be from 35% to 75% on a molar basis, for the at leastone copolymer (a)(i), at least one copolymer (a)(ii), and at least onedipolymer (b) independently and for the combination of components the atleast one copolymer (a)(i), at least one copolymer (a)(ii), and at leastone dipolymer (b) in the cover composition. In another example, therange of neutralization can be from 40 to 75% on a molar basis, for theat least one copolymer (a)(i), at least one copolymer (a)(ii), and atleast one dipolymer (b) independently and for the combination of the atleast one copolymer (a)(i), at least one copolymer (a)(ii), and at leastone dipolymer (b) in the cover composition. In another example, therange of neutralization can be from 40% to 65% or from 40% to 55%, orfrom 45 to 50%, in each case on a molar basis, fir the at least onecopolymer (a)(i), at least one copolymer (a)(ii), and at least onedipolymer (b) independently and for the combination of components (a)and (b) in the cover composition. The range of neutralization of the atleast one first copolymer (a)(i) and the at least one second copolymer(a)(ii) may be independent of the range of neutralization of thecomponent (a) that they form together, and the component (a) may befurther neutralized after the at least one first copolymer (a)(i) andthe at least one second copolymer (a)(ii) are combined or thecombination of components (a) and (b) may be further neutralized after(a) and (b) are combined.

The at least one first copolymer (a)(i), the at least one secondcopolymer (a)(ii), and the at least one dipolymer (b) may combined inany order, either before or after being each independently neutralizedor partially neutralized.

In one example, the non-neutralized high molecular weight firstcopolymer or first copolymers (a)(i) and low molecular weight copolymeror copolymers (a)(ii) (if any) of (a) are melt-blended and thenneutralized so that desired higher or full neutralization may beachieved in one step. The unneutralized or neutralized dipolymer ordipolymers (b) may then be added, and optionally the resulting mixturemay be further neutralized.

In any case, neutralization may be effected by treating the polymerswith a basic compound such as any of those already mentioned. The basiccompound(s) may be added neat to the polymer(s) or they may be premixedwith a polymeric material, such one of the acid polymers of (a) or (b),for example with a second copolymer (a)(ii), to form a “masterbatch”that may be added to the remaining copolymers to form the polymericportion or cover composition.

Another example involves melt blending the pre-neutralized component (a)and component (b) with the same or different neutralizing agents to thesame or different degrees of neutralization at the desired blend ratiosto achieve the cover compositions.

In addition to the thermoplastic polymeric portion, the covercompositions may further comprise small amounts of optional materialscommonly used and well known in the polymer art, such as conventionaladditives including reinforcing chopped fibers, aramide fibers andmicropulps, organo-clays to achieve exfoliated nano-platlets,nano-silicas, or other fillers to further enhance the mechanicalproperties, such as stiffness, scuff resistance, wear resistance;plasticizers; stabilizers including viscosity stabilizers and hydrolyticstabilizers, primary and secondary antioxidants such as for exampleIRGANOX™ 1010, and ultraviolet light absorbers; anti-static agents;dyes, pigments such as titanium dioxide, or other coloring agents, andoptical brighteners; fire-retardants; lubricants, processing aids, slipadditives, antiblock agents such as silica or talc, release agents; andso on, which may be used in any combination.

These conventional additives may be present in the cover in quantitiesthat are generally from 0.01 to 15 weight %. The conventional additivesmay be present in quantities of from 0.01 to 5 weight % based on thetotal weight of the composition. The conventional additives may bepresent in quantities of from 0.01 to 10 weight %, based on the totalweight of the cover. The quantity of conventional additives is selectedto not detract from the basic and novel characteristics of the cover andto not significantly adversely affect the performance of the cover ofthe golf ball.

The incorporation of these optional materials into the cover may becarried out by any known process, for example, by dry blending, byextruding a mixture of the various constituents, by the conventionalmasterbatch technique, or the like.

The thermoplastic composition including the polymeric portion for thecover may be formulated with a pigment, such as a yellow or whitepigment, and in particular a white pigment such as titanium dioxide orzinc oxide, an aluminum pigment, or a white pearlescent pigment such astitanium dioxide-coated mica pigments. White, silver metallic, and whitepearl colors provide dyed second colors that are truest to the dyeselected, but other first colors, particularly light colors such as alight yellow, can be used to create a different color with the dye.Generally, dark or intense first colors are avoided, but pigments ofmany colors may be used to provide light colors or for tinting, andspecial effect pigments may also be used as desired. Examples of otherpigments that could be used include inorganic pigment such as red ironoxide, transparent red iron oxide, chromium oxide green, ferric ammoniumferrocyanide (Prussian blue), and ultramarine; organic pigments such asmetallized and non-metallized azo reds, quinacridone reds and violets,perylene reds, copper phthalocyanine blues and greens, carbazole violet,monoarylide and diarylide yellows, benzimidazolone yellows, tolylorange, and naphthol orange; and flake pigments such as copper flakepigments, zinc flake pigments, stainless steel flake pigments, andbronze flake pigments, and iron oxide-coated mica pigments; andfluorescent or phosphorescent pigments such as zinc sulfide, cadmiumsulfide, and metal aluminate phosphorescent pigments. Generally titaniumdioxide is used as a white pigment, for example in amounts of from about0.5 parts by weight or 1 part by weight to about 8 parts by weight or 10parts by weight based on 100 parts by weight of resin. In variousembodiments, a white-colored cover may be tinted with a small amount ofblue pigment or brightener.

The cover may also contain one or more customary additives such asfillers, dispersants, hindered amine light stabilizers such aspiperidines and oxanilides, ultraviolet light absorbers such asbenzotriazoles, triazines, and hindered phenols, antioxidants such asphenols, phosphites, and hydrazides, plasticizers, defoaming agents,processing aids, surfactants, fluorescent materials and fluorescentbrighteners, and so on.

The cover can include a filler such as, but not limited to, choppedfibers, aramide fibers and micropulps, other pulps, organo-clays havingexfoliated nano-platlets, nano-silicas, other nano-fillers, clay, talc,asbestos, graphite, glass, mica, barium sulfate, aluminum hydroxide,calcium carbonate, magnesium carbonate, and other metal carbonates, zincsulfide, calcium metasilicate and other silicates, diatomaceous earth,carbonates, metals (such as titanium, tungsten, zinc, aluminum, bismuth,nickel, molybdenum, iron, copper, brass, boron, bronze, cobalt,beryllium, and alloys of these), metal oxides (such as zinc oxide,magnesium oxide, iron oxide, aluminum oxide, titanium oxide, zirconiumoxide and the like), particulate synthetic plastics (such as highmolecular weight polyethylene, polypropylene, polystyrene, polyethyleneionomeric resins, polyamide, polyester, polyurethane, polyimide, and thelike), particulate carbonaceous materials (such as carbon black, and thelike), as well as cotton flock, cellulose flock, cellulose pulp, leatherfiber, and combinations of any of the above.

Fillers may be used to adjust the specific gravity, modulus, and otherphysical properties of the cover. The total amount of the filler may befrom about 0.5 to about 30 percent by weight of the cover composition.Wetting or dispersing additives may be used to more effectively dispersethe pigments and particulate fillers. Generally, the additives will bepresent in the composition in an amount between about 1 and about 25weight percent based on the total weight of the cover compositiondepending upon the desired properties.

The cover may be injection molded or compression molded around the coreand any intermediate layers. The injection molding temperature maygenerally be in a range of from 150 to 250° C. Alternatively the covercan be applied by initially forming two hemispherical shells, thencovering the core with these shells and molding under applied pressureand heat.

The dimples arranged on the cover surface, while not subject to anyparticular limitation, can number from 250 to 350, or from 300 to 350,or from 318 to 328. Any one or combination of two or more dimple shapes,including circular shapes, various polygonal shapes, dewdrop shapes andoval shapes, may be suitably used. For example, when circular dimplesare used, a dimple diameter of at least about 2.5 mm but not more thanabout 6.0 mm may be suitably selected. By using from three to five ormore types of dimples, the dimples can be made to cover the sphericalsurface in a well-balanced and uniform manner. The types of dimples arenot subject to any particular limitation, although the dimples may bedisposed on the spherical surface in a polyhedral arrangement suitablefor dimple placement, such as a repeating pattern of unit polygons(e.g., unit triangles, unit pentagons). It is also possible to usedimples which all have slightly different diameters. In such a case, thenumber of dimple types may be set to twenty or more. In order to fullymanifest the aerodynamic properties, it is desirable for the ratio ofthe sum of the individual dimple surface areas, each defined as thesurface area of the flat plane circumscribed by the edge of the dimple,relative to the spherical surface area of the ball were it to have nodimples thereon to be at least 70%, or 75%.

Typically, the cover may have a thickness of from about 0.5 mm or fromabout 1 mm or from about 1.5 mm up to about 2 mm or up to about 2.5 mmor up to about 3 mm, although golf ball may also be made with covershaving a thickness of less than about 0.5 mm or up to about 5 mm.

One or more coating layers may be applied to the cover of the golf ball,and these may be pigmented or clear, thermoplastic or thermoset.

In addition to having a cover, the golf ball may have any knownconstruction. Examples include a two-piece golf ball comprising aunitary core and a cover around the core; a three-piece ball comprisinga core, an intermediate layer, and a cover layer; or a multi-layer golfball comprising more than one intermediate layer between core and cover.The core of the golf ball may be solid, semi-solid (e.g., paste or gel),hollow, or filled with a fluid or powder in a one-piece or multi-piececonstruction. As used in describing the core, a fluid may be a liquid,paste, gel, gas, or some combination of these. The core and anyintermediate layer or layers may be made from known golf ball materials,including thermoset elastomers, thermoplastic elastomers, and ionomers.Nonlimiting examples of thermoset elastomers include natural rubber andsynthetic rubbers such as styrene butadiene rubber, polybutadienerubber, polyisoprene rubber, styrene-butadiene rubber (SBR), andethylene-propylene-diene first copolymer (EPDM). In various embodiments,a high cis-polybutadiene crosslinked with a diacrylate such as zincdiacrylate is used for a core or intermediate layer. The highcis-polybutadiene can comprise 40-100% by weight of the cis form. Thehigh cis-polybutadiene can comprise 70-100% by weight of the cis form.The high cis-polybutadiene can comprise 90-100% by weight of the cisform. Nonlimiting examples of suitable thermoplastic elastomers aremetallocene-catalyzed block copolymers of ethylene and α-olefins having4 to about 8 carbon atoms, thermoplastic polyamide elastomers (PEBA orpolyether block polyamides), thermoplastic polyester elastomers,thermoplastic styrene block copolymer elastomers such aspoly(styrene-butadiene-styrene),poly(styrene-ethylene-co-butylene-styrene), andpoly(styrene-isoprene-styrene), thermoplastic polyurethane elastomers,thermoplastic polyurea elastomers, and dynamic vulcanizates of rubbersin these thermoplastic elastomers and in other thermoplastic matrixpolymers. The core and each intermediate layer may include fillers orother customary additives. The golf ball cores may be formed using anyconventional techniques.

The golf ball can be manufactured so as to conform with the Rules ofGolf for competitive play with a ball diameter which is of a size thatwill not pass through a ring having an inside diameter of 42.672 mm, butis not more than 42.80 mm, and to a weight of generally from 45.0 to45.93 g.

The cover made of the disclosed composition has excellent scuffresistance while providing a desirable hardness and flex modulus.

The foregoing description of the embodiments has been provided forpurposes of illustration and description. It is not intended to beexhaustive or to limit the invention. Individual elements or features ofa particular embodiment are generally not limited to that particularembodiment, but, where applicable, are interchangeable and can be usedin a selected embodiment, even if not specifically shown or described.The same may also be varied in many ways. Such variations are not to beregarded as a departure from the invention, and all such modificationsare intended to be included within the scope of the invention.

1. A golf ball having a core and a cover, wherein the cover comprises a thermoplastic polymeric portion consisting essentially of (a) (i) at least one first copolymer that has a weight average molecular weight of from about 80,000 to about 500,000 daltons and that consists of ethylene monomer units, from about 5 to about 12 percent by weight of α,β-ethylenically unsaturated carboxylic acid monomer units selected from the group consisting of acrylic acid monomer units, methacrylic acid monomer units, and combinations thereof, and from about 5 to about 40 percent by weight of at least one member selected from the group consisting of alkyl acrylate monomer units, alkyl methacrylate monomer units, and combinations thereof; (ii) at least one second copolymer that has a weight average molecular weight of from about 2000 to about 30,000 daltons and that consists of ethylene monomer units and from about 3 to about 25 percent by weight of α,β-ethylenically unsaturated carboxylic acid monomer units selected from the group consisting of acrylic acid monomer units, methacrylic acid monomer units, and combinations thereof, wherein (a)(i) is from about 80 to 100 percent by weight of the sum of the weights of (a)(i) and (a)(ii) and (a)(ii) is from 0 to about 20 percent by weight of the sum of the weights of (a)(i) and (a)(ii); and (b) at least one dipolymer that has a weight average molecular weight of from about 80,000 to about 500,000 daltons and that consists of ethylene monomer units and acrylic acid monomer units, wherein the at least one dipolymer has a molar fraction of the acrylic acid monomer units that is within ±about 10% of a molar fraction of the α,β-ethylenically unsaturated carboxylic acid monomer units of the at least one first copolymer (a)(i); wherein (b) is from about 10 to about 90 percent by weight of a combined weight of (a) and (b), and wherein from about 30% to about 75% on a molar basis of total acid groups of (a) and (b) are neutralized with cations selected from the group consisting of magnesium cations, calcium cations, zinc cations, and combinations thereof.
 2. A golf ball according to claim 1, wherein the at least one first copolymer (a)(i) has from about 8 to about 12 percent by weight of α,β-ethylenically unsaturated carboxylic acid monomer units.
 3. A golf ball according to claim 1, wherein the at least one dipolymer (b) has a molar fraction of acrylic acid monomer units within ±about 5% of the molar fraction of α,β-ethylenically unsaturated carboxylic acid monomer units of the at least one first copolymer (a)(i).
 4. A golf ball according to claim 1, wherein the at least one dipolymer (b) has a molar fraction of acrylic acid monomer units within ±about 3% of the molar fraction of α,β-ethylenically unsaturated carboxylic acid monomer units of the at least one first copolymer (a)(i).
 5. A golf ball according to claim 1, wherein the weight average molecular weight of the at least one first copolymer (a)(i) is from about 200,000 to about 400,000 daltons and the weight average molecular weight of the at least one dipolymer (b) is from about 200,000 to about 400,000 daltons.
 6. A golf ball according to claim 1, wherein from about 50% to about 100% on a molar basis of the neutralizing cations are selected from the group consisting of magnesium cations, calcium cations, and combinations thereof.
 7. A golf ball according to claim 1, wherein the at least one member of (a)(i) comprises n-butyl acrylate monomer units.
 8. A golf ball according to claim 1, wherein the α,β-ethylenically unsaturated carboxylic acid monomer units of the at least one first copolymer (a)(i) are acrylic acid monomer units.
 9. A golf ball according to claim 1, wherein the α,β-ethylenically unsaturated carboxylic acid monomer units of the at least one second copolymer (a)(ii) are acrylic acid monomer units.
 10. A golf ball according to claim 1, wherein (a)(i) is 100 percent by weight and (a)(ii) is 0 percent by weight of the sum of the weights of (a)(i) and (a)(ii).
 11. A golf ball according to claim 1, wherein from about 50% to about 100% on a molar basis of the neutralizing cations are calcium cations.
 12. A golf ball according to claim 11, wherein 100% on a molar basis of the neutralizing cations are calcium cations.
 13. A golf ball according to claim 1, wherein the cover has a thickness of from about 1 mm to about 3 mm.
 14. A method of manufacturing a golf ball having a core and a cover, comprising: forming the cover around the core from a thermoplastic polymeric portion consisting essentially of (a) (i) at least one first copolymer that has a weight average molecular weight of from about 80,000 to about 500,000 daltons and that consists of ethylene monomer units, from about 5 to about 12 percent by weight of α,β-ethylenically unsaturated carboxylic acid monomer units selected from the group consisting of acrylic acid monomer units, methacrylic acid monomer units, and combinations thereof, and from about 5 to about 40 percent by weight of at least one member selected from the group consisting of alkyl acrylate monomer units, alkyl methacrylate monomer units, and combinations thereof; (ii) at least one second copolymer that has a weight average molecular weight of from about 2000 to about 30,000 daltons and that consists of ethylene monomer units and from about 3 to about 25 percent by weight of α,β-ethylenically unsaturated carboxylic acid monomer units selected from the group consisting of acrylic acid monomer units, methacrylic acid monomer units, and combinations thereof, wherein (a)(i) is from about 80 to 100 percent by weight of the sum of the weights of (a)(i) and (a)(ii) and (a)(ii) is from 0 to about 20 percent by weight of the sum of the weights of (a)(i) and (a)(ii); and (b) at least one dipolymer that has a weight average molecular weight of from about 80,000 to about 500,000 daltons and that consists of ethylene monomer units and acrylic acid monomer units, wherein the at least one dipolymer has a molar fraction of the acrylic acid monomer units that is within ±about 10% of a molar fraction of the α,β-ethylenically unsaturated carboxylic acid monomer units of the at least one first copolymer (a)(i); wherein (b) is from about 10 to about 90 percent by weight of a combined weight of (a) and (b), and wherein from about 30% to about 75% on a molar basis of total acid groups of (a) and (b) are neutralized with cations selected from the group consisting of magnesium cations, calcium cations, zinc cations, and combinations thereof.
 15. A method according to claim 14, wherein the step of forming the cover comprises forming the cover to have a thickness of from about 1 mm to about 3 mm. 